Microstructural investigation of subcritical crack propagation and Fracture Process Zone (FPZ) by the reduction of rock fracture toughness under cyclic loading

Cyclic and Fatigue Behaviour of Rock Materials: Review, Interpretation and Research Perspectives

“…12. Scanning electron microscope observations are compared in both cases (Erarslan 2016). For monotonic loading, almost all grains on the failure surface are highly cracked and failure mode is brittle.…”

“…For cyclically loaded specimens, most grains are cracked-free and failure holds along their boundaries. The primary fatigue mechanism is identified as inter-granular cracks (Erarslan 2016;Erarslan and Williams 2012a). A secondary mechanism results in wear and shearing between rock grains starting at contact points.…”

“…Several studies on Brisbane tuff state that a lot of dust and fragments are created during indirect tensile cyclic loading (Erarslan and Williams 2012b;Erarslan et al 2014;Erarslan 2016;Ghamgosar and Erarslan 2016;Ghamgosar et al 2017), while a clear and clean crack is observed during monotonic tests. This comparison is reproduced in Fig.…”

“…In this figure, consequences of the two ongoing mechanisms are clear. Cyclic loading induces a wider fracture process zone and branching of the crack, resulting in plastic deformation measured at macroscale (Le et al 2014;Ghamgosar and Erarslan 2016;Erarslan 2016).…”

“…In addition, they are necessary to calibrate advanced constitutive laws. Indirect tensile tests are also carried out to investigate more deeply the fundamental fatigue fracture process or estimate the tensile strength of a material (Erarslan and Williams 2012b;Erarslan et al 2014;Ghamgosar and Erarslan 2016;Wang et al 2016;Erarslan 2016).…”